De-mystifying Heat Pumps

(save 50% on heating and cooling costs and get a $500 rebate from Efficiency Maine

Office of Sustainability, Unity College

December 15, 2014

What is a heat pump? Your refrigerator is a heat pump. It moves heat from inside the unit to the outside, thus cooling the interior (and warming the room – hence the fan and the recommendation to clean your coils periodically). If you could reverse the direction of heat flow, it would be a heat pump heating your refrigerator just like it was your home.

 There are two main types for residential and commercial applications:

1) Air source heat pumps extract heat from the outside air down to about -15 degrees (yes, minus 15 degrees F) and pump it into your house;

2) Ground-source heat pumps (often erroneously called ‘geothermal heat pumps’) extract heat from water in the ground (groundwater in Maine has a temperature typically of 45 to 55 degrees) and pump it into your house (the term ‘geothermal’ is best used to describe the water from geologic activity in Finland or Yellowstone National Park).

Both types of heat pumps are 200% to 300% efficient compared to fossil-fuel fired units. This efficiency is because heat pumps move heat from placed to place rather than creating heat.

Air source heat pumps only need air to heat your home; ground source heat pumps require a water well (or wells) to function. Air source heat pumps work silently, ground source heat pumps are typically noisy. All air source heat pumps (and some ground source heat pumps) also provide air conditioning as a side benefit.

Cost: Air source heat pumps cost $1,500 to $4,000 and one or two of them can heat a well-insulated typical home. Ground source heat pumps cost $20,000 to $40,000 and can heat an average size home, not counting the cost of drilling wells.

Both Unity House and Terrahaus have air source heat pumps as their main source of heat. Air source heat pumps are being considered for Unity 2, the (new) new residence hall.


  1. Low-cost heat – The cost of heating with a heat pump is about half the cost of heating with oil, kerosene, electric baseboard or propane.

2.  Comfort – With advances in controls, heat pumps can maintain very constant temperatures.

3. Safety – Because heat pumps are electrically powered, there is no risk of combustion gas leaks.

4. Air quality – Heat pumps filter air as they heat or cool.

The only consideration for homeowners is that the units become less efficient as the outside temperatures drop. For example, a unit that delivers four units of heat for every unit of electricity at 50°F, may only deliver two units of heat for every unit of electricity at -15°F. If the temperature drops low enough, the system may turn off completely. For this reason, air-source heat pumps are often coupled with your existing source of heat or with a back-up wood stove.

A hybrid what?!? Domestic hot water options for Mainers

There are great options when making choices for your future domestic hot water – and none of them include fossil fuels.  Even better, the cost of equipment for non-fossil fuel hot water almost always qualifies for rebates from Efficiency Maine.   If your hot water heater is in need of replacement, don’t fall for the recommendation from your oil or propane dealer to replace it with their fossil fuel fired equipment!   Go electric or hybrid especially if you can combine it with solar at some time in the future.   Save money and reduce your carbon footprint.

In the table below, note the new technology called ‘hybrid electric hot water’ which is a heat pump augmented with electric back-up.  A hybrid water heater can reduce your hot water bill by 30% to 50%.  Substantial rebates from Efficiency Maine and sometimes additional rebates from retailers can greatly reduce the cost of a hybrid water heater.  Note that hybrid water heaters are expected to be the domestic water source in the new Unity 2 residence hall.

Equipment costs are not listed here because the technology and costs are evolving and the rebates change frequently.

A cost comparison of domestic water heating options for Maine
example annual cost of
 description cost, family of 4 energy (units)
1 solar with electric hybrid water heater back-up $                   180 0.14 KWH
2 solar with electric back-up $                   210 0.14 KWH
3 solar with oil boiler coil back-up $                   225 3.20 gal
4 electric hybrid hot water heater $                   525 0.14 KWH
6 standard electric hot water heater $                   725 0.14 KWH
7 propane (instantaneous tankless water heater) $                   700 2.90 gal
8 oil (direct fired tank storage) $                   735 3.20 gal
9 oil (direct fired internal coil heater) $                   835 3.20 gal
10 propane (direct fired tank storage) $                   900 2.90 gal
adapted from Efficiency Maine (


The $400 billion building energy conundrum: why occupants matter

The US spends $400 billion to power buildings each year, about 50% of the total energy use in the country.  Reducing energy waste in these buildings would save billions, reduce carbon dioxide emissions, create jobs, and reduce reliance on fossil fuel imports, not to mention increase resiliency for the economy and individual businesses by insulating them from energy price shocks such as the recent spike in natural gas prices.

The opportunity for campuses to model best practices is paramount to stimulating change from the bottom-up.  One way to reduce costs and energy use: better education of the occupants.

It turns out that people-powered energy efficiency can make quite an impact.   I was an undergraduate during the 1973 oil embargo.   We held competitions among dorms to reduce electrical use, and the campus dorms saved 26%.   Companies doing aggressive employee education programs have achieved 10 to 15% energy reductions, which at Unity College would equate to $20,000 to $30,000 per year.   Energy efficiency solutions already within our grasp can make a huge difference.

Remember, there are no net-zero energy buildings, by definition.   There are net-zero energy occupants of buildings!  People matter.

There is no silver bullet for energy costs or carbon dioxide reduction.  Instead campuses should be looking for ‘silver buckshot’ solutions.   Many little actions will result in big changes – and big savings.  The next step: these changes will require leadership from the top at campuses everywhere.


Its about time: more companies committing to 100% renewable power

In a press release this week, Amazon became the latest tech company to commit to 100% renewable power.  Apple, Facebook, Google, SalesForce, and Box have already stated that they intend to achieve a goal of procuring100 percent renewable energy.   Apple is the largest private owner of solar facilities in the US.

Its the wave of the future for economic, environmental, and marketing reasons.  Eventually this wave will result in fossil fuel investments becoming de-valued ‘stranded assets’, solving the perceived CO2 climate crisis.

While Google, Facebook, Box and Salesforce are predominately software companies, Amazon’s massive e-commerce operations make it a prime candidate for sustainability efforts.

As prices for solar, wind and other renewables continue to fall, large companies in industries like retail — such as IKEA and WalMart— have also announced major initiatives to add rooftop solar.  Projected ongoing increases in the price of electricity in 2014-15 add additional economic incentive to the mix.

If major companies with huge power needs can do it, the question is, when will the first college campus announce 100% renewable power generated on its own campus?

Worth hearing again, and again, and again….

Get it done.

Anyone want to go to Paris?

Students currently enrolled at Unity College are privileged

Sustainable You(nity)

by Gunnar Norback (Earth and Environmental Science major, Class of 2017)


In 2012, Unity College became the first institution of higher education in the nation with an investment portfolio completely divested from fossil fuels. America’s Environmental College led the charge for higher education to invest in the future of students, a future built around renewable energy sources. Now time arrived for for the Unity College campus to follow in the footstep of its endowment, reducing greenhouse gas emissions and implementing renewable energy.

A strategic plan adopted by the Unity College Board of Trustees in 2014 sets the institution on track to be a carbon dioxide neutral campus by 2020. This model supersedes the national plan proposed by the EPA to reduce carbon dioxide emissions in the United States by only 30% by 2030. Unity College is again ready to set the standard and lead the charge for academia to make the right decision.

Photovoltaic arrays, commonly referred to as solar panels, are a cost effective and efficient manner of meeting the institutions energy needs. PV will be incorporated into new construction as well as retrofitted to meet the needs of existing facilities. The existing 35 kilowatt PV array affixed to Unity’s Quimby Library produces 42,000 kilowatt hours annually, providing the school with $5,880 of energy each year.

Large scale adoption of a photovoltaic array as the primary source for electricity for Unity College will produce more than the 1 million kilowatt hours used annually by the institution. PV panels will be installed on south facing roofs, ground mounted in unused fields as well as strategically placed near classroom facilities to allow ease of access for educational purposes.

Once the photovoltaic infrastructure is in place, oil furnaces can be decommissioned in existing structures to be replaced by pellet boilers and electric air-source heat pumps. Further progress and renovation in existing structures will be made according to the specifications and needs of each.

The mission of Unity College provides a liberal arts education through the framework of sustainability. The development of cutting edge energy solutions on campus will provide access to Unity College students for relevant experience in the field of sustainability science, which can be applied upon graduation.

Students currently enrolled at Unity College are privileged to be here now.  The time has come where change must be made, the institution has charted a course investing in the future of the world’s youth, each and every Unity College students holds a key role in this investment. Unity College students will capitalize on this opportunity to align their values as well as careers with mitigating the effects of the most pressing issue of today: climate change.

Acting locally; check your tire pressure to reduce climate change (and oh by the way, save money)

Did you know?

Your tire pressure drops about 1 PSI for every 10 degree drop in temperature.  That means that by winter, your tires could be underinflated by 6-8 PSI compared to this summer – which could be 25% underinflated.  Six PSI can reduce your gas mileage by as much as 3 mpg — or even more if you drive a car that gets high gas mileage.  85 percent of drivers surveyed do not check their tire pressure regularly according to the Rubber Manufacturers Association.

So, one cool morning this weekend, check and adjust your tire pressure before you drive your car(s).  Save money – AND reduce CO2 emissions!


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